Various coating methods are used in the semiconductor industry, such as centrifugal coating and spray coating.
In centrifugal coating, a substance to be applied is deposited on a substrate in liquid form. Afterwards, the substrate is set into rotation. The rotation generates the action of a force on the liquid and distributes it over the entire surface of the substrate. By a dedicated choice of the coating parameters, primarily the rotational speed and rotational acceleration of the carrier substrate, layer thicknesses from a few nanometers to a few micrometers, and in extreme cases even a few millimeters, can be produced. The centrifugal coating is used primarily for coating of flat surfaces with a resist or cement which is used in the semiconductor industry for cementing of several substrates. The advantage lies in the very precise, prompt, efficient and economical application of the material. The disadvantage of centrifugal coating appears, however, in structured substrates or very large substrates. Structured substrates lead to a relatively inhomogeneous thickness of the layer to be applied, mainly when the target layer thickness is smaller than the highest topographies on the substrate. In this respect, as a result of the material being distributed from the inside to the outside, only the side walls of the topographies oriented to the center are coated with the material, and conversely bubbles or faults form in the material on the sides facing away from the center. Another disadvantage of centrifugal coating consists mainly in the maximum size and limitation with respect to the geometrical shape of the substrates which are to be coated. Standardized substrates, primarily wafers, in most cases silicon wafers, have a round, therefore radially symmetrical symmetry and a standardized diameter. In the past substrates with diameters from two to twelve inches were used. In the future, substrates with diameters of up to eighteen inches will probably be used in the semiconductor industry. In addition, there are very many branches of industry which are dependent on coating rectangular substrates which are many times larger than the indicated radially symmetrical substrates. For example, in the solar industry, substrates, i.e., panels must be coated. These panels are not round and would not fit into a conventional coating system for centrifugal coating. In this respect, the panels are rectangular substrates whose length and/or width is/are often greater than two meters. Their thickness is in the millimeter to centimeter range. Similar problems arise for all types of substrates, generally glass substrates, which are used for windows, displays, windshield, etc.
One possibility for the coating of these panels is spray coating. With a correspondingly designed system for spray coating, the panels, preferably even in an assembly line process, are coated over the entire surface with any material. The deciding criterion for optimum coating is mainly the homogeneity of the layer thickness. The panel must be coated with a material over its entire area, which area is not small for the use of spray coating systems. The layer thickness of the deposited layer must often be in the micrometer or even nanometer range. Industry has already found different approaches for corresponding situations. Thus, several nozzles can be distributed along the entire width of a corresponding spray coating system, wherein each nozzle coats only a small strip of the panel which lies directly under it. In this arrangement, the problem arises that the finely atomized particles agglomerate along the “interfaces” at which the coating areas of the nozzles intersect. As a result, a homogeneous layer thickness of the layer cannot be assumed. Another already implemented possibility consists in using one or more nozzles which move back and forth along a rail along the entire width of the coating system over the panel to be coated. This version definitively produces a layer with a more homogeneous layer thickness than in the first configuration, but it is comparatively slow and is not suited for a high throughput. The bearing units, the rail and the carriages on which the nozzle is fastened are accordingly movable and thus susceptible to wear and high failure probabilities. Corresponding vibrations and/or turbulence, which massively influence the homogeneity of the layer, are formed by the movement of the nozzles.
US 2010/0078496 shows a spray nozzle apparatus in which a spray mist of a corresponding spray coating system is deflected.
The goal of this invention is to devise a spray nozzle apparatus and a corresponding system and a method for operating a spray nozzle apparatus with which a more homogeneous coating is enabled.
This goal is achieved with the features of the claims. Advantageous developments of the invention are given in the dependent claims. All combinations of at least two of the features given in the specification, the claims and/or in the figures fall within the scope of the invention. For given values ranges, values which lie within the indicated limits should be considered disclosed as boundary values and able to be claimed in any combination.